High frequency luminous tube



NQ/ T w w W 0 o w w% A04 5 5 mi R. R. MACHLETT ET AL HIGH FREQUENCY LUMINOUS TUBE Filed July 9, 1927 5/ L (I: f

50 MMF Aug. 18, 1931.

Patented Aug. 18, 1931 UNITED STATES PATENT OFFICE RAYMOND ROBERT MACHLETT AND JOHN FRASER STOKES, OF NEW YORK, N. Y.,

ASSIGNOB-S TO RAINBOW LIGHT, IN

0., A CORPORATION OF NEW YORK HIGH FREQUENCY LUMINOUS TUBE Application 'filed July 9, 1927. Serial No. 204,480.

Our invention relates to improvements in high frequency luminous tubes containing a rarefied gaseous atmosphere which is caused to become brilliantly luminescent upon the a passage of an electric current through the same. We prefer to use neon gas for this purpose, owing to its attractive red color and to its exceptionally good electrical conducting characteristics. A combination of argon and mercury vapor may also be used,

if blue and green effects are desired.

It has been heretofore proposed to o erate luminous discharge tubes by means 0 high frequency currents passed longitudinally through the tube either by means of interior or exterior electrodes. The results secured with such arrangements have not been satisfactory, since it does not seem to be possible within commercially practicable limits to generate high frequency currents of sufficient value to produce useful light and at the same time of suflicient potential to operate the conventional or usual type of luminous tube in which the terminals are located at the extreme ends of a long tubular structure.

This is particularly true where the attempt has been made to use vacuum tube oscillators energized from the ordinary 110 volt supply.

By means of our present invention we are able to produce a satisfactory illumination from luminous tubes and at the same time to employ a vacuum tube oscillator as the source of the high frequency currents. This makes an extremely desirable commercial arrangement, since a vacuum tube oscillator is not only inexpensive but is automatic in operation and operates without any attention whatever for a long period of time. Therefore, the invention is adapted especially for use in connection with electric signs, the tubes being in the form of letters or symbols. With our present invention, instead of passing the current longitudinally through a long gaseous tube with terminal electrodes,

4 we secure illumination by passing electric energy through the tube in a direction normal to its axis, thereby securing a minimum path and thus permitting current of minimum voltage to be employed.

In this way it no longer becomes necessary to make up a sign by taking a very long tube and bending it in various directions to form letters or symbols so as to spell out complete words. With our invention each letter may be separate and self-contained and operate as a separate unit, although, of course, they may be connected together, if desired. Thus, it becomes possible to make up standard letters and to assemble them in any desired arrangement to constitute the completed sign, the commercial advantages of which are obviouse Furthermore, a long tube bent into the "form of several letters presents not only a commercially expensive product, but a very fragile one. Separate, self-contained letters or symbols as we propose are relatively strong and sturdy.

In the manufacture of a sign from a single long tube it is almost always necessary in some portions of the sign for the tube to lie in different planes, but with our improvements the separate individual letters or symbols are simply bent into the desired form in a single plane.

Finally, in the case of a long tube bent into the form of several connected letters or symbols, should the tube break or fail for any reason, it becomes necessary to reprocess the entire tube and to again fill it with the desired gas. With our improvements, if a single letter or s mbol fails, it alone requires to be reprocessed With our present improvements we employ two plates of a condenser which are, respectively, connected to points in an oscillating circuit where a sufiicient potential difference exists, and the vessel, letter, symbol, or other tube containing the gas to be illuminated is interposed between the condenser plates and O0 tainer for the gas and to employ a frequency of a very high order. Excellent results have en secured with glass walls of: a thickness of half a millimeter or less. The invention may be carried out in various ways and a number of examples are illustrated in the accompanying drawings forming part of this specification and in which Figure 1 is a cross-sectional view through a luminous tube showing one of the condenser plates located axially within the tube,

the other condenser plate being located on the exterior of the tube;

Figure 2 is a longitudinal section on the line 2-2 of Figure 1;

Figure 3 is an elevation showing a separate self-contained tube in the form of a letter held between-two condenser plates of metallic gauze, in order that the luminous effect may be observed through the plates. This is the preferred arrangement.

Figure 4 is a cross-sectional view on line 4-4 of Figure 3;

Figure 5 is an elevation of another arrangement in which the tube is formed with double parallel walls and is mounted in and supthe 36 ported by a metal support forming one of the condenser plates, the other condenser plate being located between the parallel walls of the tube;

Figure 6 is a section on the line 66 of 0 Figure 5; and

Figure 7 is a diagram showing a conven tional oscillating circuit employing a vacuum tube and illustrating the preferred location of the condenser plates in operating our improved luminous tubes.

In all of the above-views corresponding parts are represented by similar characters. Referring first to Figure 7 an ordinary three electrode vacuum tube 1 is shown having filament 2, grid 3 and plate 4. The plate circuit is supplied with current at 350 volts, while the filament current is 6 volts. These values are merely illustrative. Suitable and ordinary transformers for this purpose are used. Radio frequency choke coils 5-5 are also shown in the plate-grid circuit," in order to confine the high frequency oscillations to the oscillating circuit. The oscillating circuit is provided with an inductance 6 and with adjustable condensers 77, the values of which are so chosen as to given oscillations of the desired frequency. As we have pointed out, frequencies of the order of 1.000 kilo- 5 cycles have been found to give satisfactory commercial results.

Connected across the oscillating circuit at points of sufiicient potential therein are conductors 8 and 9 connected to the condenser plates 10 and 11. Between the condenser plates 10 and 11 is shown a luminous tube 12 having a rarefied gas such as neon therein. It will be observed that this tube with its gas content functions practically as a dielectric, providing a current path transverse to the axis of the tube and therefore of minimum length. In practice, when the oscillator operates, the tube will become brilliantly luminescent.

Referring now to Figures 1 and 2, the tube 12 will be bent into the form of a letter or symbol or, if desired, into a plurality of letters or symbols and one of the condenser plates 10 will be located axially within the tube, the conductor 8 leading out through the tube walls in the usual way. The other condenser plate 11 is formed of a wire gauze preferably copper of relatively coarse mesh and is secured to the outside of the tube, being suitably cut to correspond with the let'- ter or symbol. An illumination will be observed through the gauze plate, and will be limited by the area thereof. In other words, with the arrangement of Figures 1 and 2, the entire gas contents of the tube will not become luminescent, but only such portion thereof as lies between the two condenser plates.

With the arrangement of Figures 3 and 4 the condenser plates 10 and 11 are both preferably made of wire gauze of coarse mesh, preferably copper, in order that the sign may be observed from both sides. This, however, is not necessary, because if the sign is to be observed only from the front, only one of the condenser plates need be of wire gauze. With this arrangement the luminous tube 12 comprises simply a glass tube bent into the form of a letter or symbol and containing the rarefied gas. It is not necessary that the tube should be a continuous tube from end to end as is the case when terminal electrodes are employed. It is only necessary that the tube shall be self contained and be provided with the desired rarefied gas. The arrangement of Figures 3 and 4 we consider to be the preferred form of our invention, because it is simple and very effective. The several luminous tubes will be supported by the condenser plates, thus doing away with the necessity of employing elaborate 'mountings as is necessary with long tubes with terminal electrodes.

Referring to the arrangement of Figures 5 and 6, it will be noted that the luminous tube 12 is provided with parallel legs or, in other words, the structure is practically a double tube. With this arrangement the condenser plate 10 closely surrounds the letter or symbol while the condenser plate 11 is located in the space between the parallel members of the letter or symbol. These plates will be cut out so as to accurately fit and support the tube. With this arrangement the elec' rical force is from edge to edge rather than from surface to surface as with the forms of the invention shown in Figures 1 and 4, inclusive.

Having now described our invention, what we claim as new therein and desire to secure by Letters Patent is as follows:

1. In a luminous tube, the combination with a source of high frequency electric oscillations constituting the entire electrical supply, and two condenser plates receiving energy therefrom, of an electrodeless gas filled luminous tube arranged with respect to said condenser plates to provide a path of minimum length for the oscillating current, perpendicular to the longitudinal axis of the tube, at least one of said plates having a length at least equal to the overall length of said luminous tube.

2. In a luminous tube, the combination with a source of high frequency electric oscillations constituting the entire electrical supply, and two condenser plates receiving energy therefrom, of an electrodeless gas filled luminous tube arranged between said condenser plates and acting as the dielectric whereby current traverses the tube in a direction normal to its length, at least one of said plates having an area at least as great as the overall area of said tube.

3. In a luminous tube, the combination with a source of high frequency electric oscillations and two condenser plates receiving energy therefrom, one of said plates being perforated to permit passage of light therethrough, of a luminous tube interposed between the condenser plates and acting as the dielectric.

4. In a luminous tube, the combination with a source of high frequency electric oscillation and two condenser plates receiving energy therefrom. of a gas filled luminous tube between said plates and mechanically supported by the same.

5. In a luminous tube, the combination with a source of high frequency electric oscillations, a perforated condenser plate, and a second condenser plate, both of said plates receiving electric energy from the source of oscillation, of a luminous tube between said condenser plates and mechanically supported by the same.

6. In a luminous tube, the combination with a source of high frequency electric oscillations constituting the entire electrical supply, and two condenser plates connected to said source at points of greatest potential,.of an electrodeless luminous tube located between said condenser plates and acting as the dielectric, the longitudinal axis of the tube being parallel to the planes of said plates and said plates having an overall area at least as great as the overall area of said tube.

7 In a luminous tube, the combination with a source of high frequency electric oscillations constituting the entire electrical supply, of a separate isolated electrodeless gas filled tube in the form of a letter or symbol deriving energy capacitatively from said source and through a path of minimum length perpendicular to the longitudinal axis of the tube, the current flowing through all portions of the tube along said path.

8. In a luminous tube, the combination with a vacuum tube oscillator, and associated oscillating circuit of high frequency, and two condenser plates deriving energy therefrom, one of said condenser plates being perforated, of a gas filled luminous tube between said condenser plates and mechanically supported by the same.

9. An illuminating device comprising the combination of a source of high frequency electrical oscillations, a pair of fiat condenser plates connected to said source and lying in parallel planes, and an electrodeless luminous discharge tube disposed between said plates, at least one of said plates having an overall area at least as great as the overall area defined by the outlines of said tube.

10. An illuminating device comprising the combination of a source of hi h frequency oscillations, a pair of spaced at condenser plates connected to said source and lying in parallel planes, and an electrodeless luminous tube disposed tube being arranged with its longitudinal axis parallel to the planes of said plates, at least one of said plates having openings therethgough for the passage of light from said tu e.

11. An illuminating device comprising the combination of a source of high frequency electrical oscillations constituting the entire electrical supply, a pair of condenser plates receivin energy therefrom, and an electrodeless gas lled luminous tube arranged with respect to said plates to provide a path of minimum .length for the oscillating current through the gas in said tube, said path lying perpendicular to the longitudinal axis of the tube, and one of said plates having a length at least as great as the overall length of the longitudinal axis of said tube.

RAYMOND ROBERT MAOHLETT.

JOHN FRASER STOKES.

between said plates, said 

